Passenger car motor vehicles have for many decades featured movable side door glass. A mechanism is required in order to move the glass between the upper closed position and the lower opened position. These mechanisms are generally known as window regulators. Window regulators can be manually operated by, or can be driven by a powered actuator, most commonly an electric motor. One type of window regulator uses a pulley arrangement using a metal cable wrapped around a drum driven by an electric motor. This device uses a carrier which engages the door glass and fastens it to the window regulator assembly to control its motion as it moves vertically.
Window regulator mechanisms can still be categorized into a group which includes dual rail and single rail types. In a dual rail system, a pair of separated rails is provided which each include a movable window clamp which is fastened to the lower edge of the glass and move in a synchronized manner to raise and lower the glass. In a single rail type, a single rail is positioned near the center of the glass panel and includes a carrier plate with a clamp assembly which engages a lower portion of the window. The carrier plate with the clamp assembly moves the window vertically along the rail between the open and closed positions. A single-rail window regulator requires fewer parts than a dual rail system, but it poses design challenges in providing sufficient stability for the control of the glass motion since it is controlled by a single rail and a single carrier plate.
For example, typical single-rail window regulators need to provide a very close fit between the carrier plate and the guide rail to reduce an angular tilt of the carrier plate in order to overcome the torque created by friction between the glass panel and the window frame, in which the glass panel is guided. Thus, the carrier plate needs to be rigid and tightly guided on the single guide rail. This requires a high material strength of the carrier plate and a firm securement of the clamp assembly to the glass panel.
If the necessary high precision and strength of the connection between the carrier plate and the guide rail is not met or is reduced due to wear, such an arrangement affects the quality of the glass guidance system and may on occasion cause undesirable noise.